Study on flavonoid and bioactivity features of the pericarp of Citri Reticulatae 'chachi' during storage

The mature pericarp of Citri Reticulatae 'Chachi' (PCRC) is one of the six traditional Chinese medicinal materials that should be used after long storage, and it was regarded that the longer the medicine was stored, the better. However, the aging mechanism of the medicine is not clear. To further investigate the effect of aging on the main active flavonoids of PCRC, ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS) and metabolomics analysis were used to analyze the flavonoids of PCRC stored for different periods. In the results, 219 flavonoids were detected. 5,7,3',4',5'-pentamethoxy dihydroflavone and 2'-hydroxy-3,4,5,3' 4',6'-hexamethoxychalcone were found from PCRC for the first time. According to the clustering analysis of metabolites, aging times of 0 year, 1 year, and 2 year were clustered into one group, and aging times of 3 year, 4 year, and 29 year were clustered into the other group. Quantitative analysis showed that the former group contained a greater amount of 4 flavonoids than the latter group, while the latter group contained a greater amount of 15 poly-methoxyflavonoids. The newly harvested PCRC was compared with the other 5 groups of PCRC (stored for 1, 2, 3, 4, and 29 years). Eight flavonoids, tectochrysin, apigenin, 2'-hydroxyisoflavone, luteolin, 6-hydroxyluteolin, gallocatechin, quercetin -O- acetylhexoside and apigenin -7-O-[beta-D-glucuronide (1 -> 2) -O-beta-D-glucuronide], were used as marker components to discriminate newly harvested PCRC and aging PCRC. In addition, the antioxidant potency composite index (APC) indicated that the PCRC stored for three or four years had stronger antioxidant activity than the PCRC stored for other periods. By means of molecular docking, it was reviewed that the amount of antiviral components against SARS-CoV-2 in freshly harvested PCRC was significantly higher than that in aging PCRC. The results in this study supplied scientific data for quality control, evaluation, and rational utilization of PCRC and basic information for further analysis of the metabolic regulation of the active components of the PCRC. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of King Saud University.